Gas-fractionating system



Aug. 4, 1959 J. VAN DER STER 2,897,656

GAS-FRACTIONATING SYSTEM Filed Oct. 27, 1955 5 Sheets-Sheet 1 INVENTOR OHAN NE 8 VAN DER- STER AGEN g 1959 VAN DER STER 2397656 GAS-FRACTIONATING SYSTEM Fled Oct. 27, 1955 5 Sheets-Sheet 2 FIG.3

INVENTOR JOHANNES VAN DER STER AGENT g 1959 J. VAN DER STER 2897656 GAS-FRACTIONATING SYSTEIM Filad Oct. 27, 1955 5 Sheets-Sheet 3 INVENTOR JOHANNES VAN DER STER AGEN Aug. 4, 1959 Filed Oct. 27, 1955 J. VAN DER STER GAS-FRACTIONATING SYSTEM 5 Sheets-Sheet 4 INVENTOR JOHANNES VAN DER STER AGEN Aug. 4, 1959 VAN DER STER 2897656 GAS-FRACTIONAIING SYSTEM Filed 0ct. 27, 1955 5 Sheets-Sheet 5 FIG.7

XNVENTOR e JOHANNES VAN DER STER GEN GAS-FRACTINATNG SYSTEM Johannes van der Ster, Emmasingei, Eindhoven, Nether lands, assignor, by mesne assignments, in North American Philips Company, lnc. New Yorir, N.Y., a corporatien Delaware Application Octoher 27, 1955, Serial No. 543,218

Claims priority, application Netherlanris March 30, 1955 Claims. (Cl. 62-49) This invention relates to gas-fractionating systems comprising a gas-fractionating column and a boiler, in which a high-boiling fraction at least partally evaporates, and furtnermore comprising a source of cold to condense the low-boilng fraction, the condensed liquid being partially supplied as washing liquid to the column and another part being drawn off from the system, whilst the column is connected with the boiler through a condut which serves for the supply of liquid and extends into the liquid inside the boiler.

With gas-fractionating systems it has been proposed to regulate the amount of thermal energy supplied to a rise pipe, through which vapeur is constantly bubbled for pumping up washing liquid, in accordance with the level of the liquid inside the boiler. Said regulation is efected in such marmer that f the level inside the boiler rises less washing, liquid is supplied to the column whereas the arnount of washing liquid increases when the level drops. This may, for example, be effected by supplying the thermal energy, which is required for maintaining the vapour-bubble pumping action, with the ad of a metal element to the rise pipe, one end of said element being secured to the rise pipe and its other end being secured to a part of the system, thus transferring thermal energy through said element to the rise pipe. In the case of an excessive rise of the level inside the boiler said elemem. is locally cooled by providing an overflow, so that less thermal energy is supplied to the rise pipe.

The invention likewise aims at regulating, in accord ance with the level of the liquid inside the boiler, of the amount of washing liquid supplied o the column. However, the solution in accordance with the present invention is diflerent.

In accordance with the invention two fmther conduts are provided between the boiler and the column to carry vapour back to the column, means beng provided for closing one of said condu'its upon a rise of the level of the liquid in the boiler, while cold is locally supplied to said condut, the amount of said flow of heat deter mining the quantity of washing liquid supplied to the column. Hence, the rate of flow of heat determines the quantity of washng liquid in the column.

The means for closing the condut may, for example, comprise a float controlled valve.

In one adv.antageous form, however, one of the conduits opens into the boiler at a lower point than does the other condut and the condut opening at a lower point into the boiler is closed by liquid upon a rise of the level of the liquid in the boiler.

Regulation may be effected in many diierent ways by means of said flow of cold. For example, the concentra tion of the fraction of high boiling point and of low boiling point inside the condut may be used as an impetus for a control device. The concentration can be measurecl inknown manner. Inthe case of fract ionating air, for example, by nieans of a magnetic oxygen meter.

to the boiler.

2.897,656 Patented Aug. 4, 1959 Alternatively, a suitbl temperature may be used as an impetus f or a control device. In one embodiment of the invention, the temperature at the wall where con densation occurs, which wall pertans to the condut opening out at a lower point into the boiler, determines the amount of washing liquid through a control mechanism.

In another embodiment, the temperature inside the condut opening into the boiler at a lower pont deter mines the amount of washing liquid through a control meehanism. In this case, consequently, the temperature is measurerl in the space of the condut. The temperatures may be measured in many diierent ways, for ex ample with the aid of a thermo-element or a. resistance thermometer. In a further embodirnent of the invention, however, the d=riving force for the control mechanism is delivered by a vapour pressure thermometer, which itself produces the force reqnred for the control.

The quantity of washing liquid supplied to the col umn is regulable in various ways by the temperature measurng devices. Thus, for cxample, a control cool; may be provided in the condut between the source of cold producing the washing liquid and the column. Al .ternatively, the washing liquid may be supplied to the column th1ouglr a rise pipe in which a vapour bubble pumping action is maintained by heating electrically and the temperature regulates the degree of heating.

When using a vapour pressure thermometer and if the gasfractionating system is used for fractionating air then oxygen, nitrogen or air may be used as vapeur in the thermometer.

Regulation may be effected not only by temperature but also by the flow of cold.

This may be eiected, in accordance with a further embodimnt of the invention, in a system in which washing liquid is supplied to the column through a rise pipe thmugh which vapour is bubbled to maintain a pumping action and which pipe is in heat-exchanging contact with the condut opening into the boiler. In accordance with a suitable embodiment of the invention, in a s ys tem comprisinga second rise pipe in which an air bubble purnping action is maintained for carrying a part of the condensed liquid o from the system and which pipe has the same down pipe as the first-mentioned rise pipe, the second rise pipe is in heat-exchanging contact with the vaponr condut opening into the boiler at a higher point. As a-matter of fact, i.t may be advisable for the condensed liquid, which is drawn off from the system, to be pumped to a given height so that the outlet is at a higher point, which permits receptacles to be easily placed below the ontiet.

As a result of the heat-transfer between the condut and the rise tube, at least part of the vapour of the high boiling point will condense. In a ;further ernbodiment of the invention, the condut opening into the boiler at a lower point advantageously comprises not only a rising part but also a down part, cold being suppliecl locally to the latter so that the vapeur and the liquid flow in the same direction. The seco nd condut may also comprise such a down p.ortion.

In order to carry ol the condensed liquid from the condut in a further embodiment of the invention, a down-part of a condut comprises an outlet condut for the condensed liquid produced in said parts, through which outlet condut said condensecl liquid is carriegl back In a furtl1er embodiment of the invention, said outlet condut should extend into the liquid inside the boiler.

In a further embodiment of the invention, a satisfactory regulation is ensured by shaping the end of" the conduitkopening at a lower point into the column in 181i9l1 manner that it is gradually closed if the liquid rises in the boiler.

The end of the conduit is preferably cut at an oblique angle in order to ensure the required gradual closure of the conduit in a simple manner.

In order that the invention may be readily carried into effect it will now be described in detail, by way of exarnple, with reference to the accompanying drawings,

in which Figs. 1 and 2 show a gas-fractionating system, in which the conduits comprise both a rising part and a down part, Fig. 2 being a cross-sectional view on the line IIII of Fig. 1.

In Figs. 3 and 4 the conduits only have a rising part, part of the condensate produced by a gas-refrigerator being carried ofi from the system through a down pipe.

Fig. 4 is a cross-sectional view on the line IVIV of Fig. 3.

In Fig. 5, the conduit opening at said lower point into the boiler comprises a vapour pressure thermometer with the aid of which the amount of condensed liquid supplied to the column is determined.

In Fig. 6 a space contains a cooling medium which is in heat-exchanging contact with the conduit opening at said lower point into the boiler.

Fig. 7 shows a gas refrigerator.

The system shown in Figs. 1 and 2 comprises a gasfractionating column 1 comprising in known manner a filler, for example Raschig rings. The system furthermore comprises a boiler 2, wherein the high-boiling fraction evaporates. Between the column 1 and the boiler 2 is provided a partition 3 through which passes a conduit 4 which extends into the liquid inside the boiler. The boiler furtherrnore comprises an outlet pipe 5 which overtops the level of the liquid and passes through the bottom 6 of the boiler. This boiler is externally provided with fins 7 having openings 8 in such a marmer that the open ings of successive fins do not register. The fins are surrounded by a wall 9 with a supply conduit 10 and an outlet conduit 11. The conduit 11 opens into the column 1 at some distance from the bottom side. The column comprises an outlet conduit 12 for the low-boiling fraction, which outlet conduit is connected with a conduit 13 leading to the condenser space of a gas refrigerator 14. This gas refrigerator is of usual type and driven from an electric motor 15. Connected to the conduit 12 is a down pipe 16 with a receptacle 17 at its lower end, which receptacle carries two rise pipes 18 and 19. The rise pipe 18 opens into the column 1 at its upper end and the rise pipe 19 with an outlet conduit 19a for the produced vapour opens by way of a down part 20 and a liquid look 21 outside the system.

The boiler 2 is connected with the column not only through the conduit 4 but also through two pipe connections 22 and 23. Besides the rising parts denoted by.22 and 23 said pipe connections also comprise down portions denoted by 24 and 25 respectively, which are coupled together through a conduit 26 and jointly open through a conduit 27 with a cock 28 into the column. The down parts 24 and 25 respectively comprise outlet conduits 29 and 30 respectively, which extencl into the liquid of the boiler. The pipe connection 23 opens into the boiler at a point lower than does the pipe connection 22 and the mentioned pipe connection has its lower end cut at an oblique angle. The down-portion of the pipe connection 23 opening at a lower point into the boiler is in heatexchanging contact with the rise pipe 18 through a conductiae strip 32 while the down portion 24 of the pipe connection 22 is connected to the rise tube 19 through a conductive strip 33.

The system operates as follows:

On starting up the gas refrigerator, a subatmospheric pressure is produced in the condenser chamber of the gas the gas-mixture to be fractionated, hereinafter air is chosen, is drawn in through the conduit 10. The air flows through the heat-exchanger consttuted by the tube 5 with fins 7 and is cooled in it due to the heat-exchanging contact of the tube 5 with the bottom 6 of the boiler 2. This boiler contains the high boiling fraction, in the present case oxygen, which evaporates due to the supply of thermal energy. Any impurities of the air, for example water vapour and carbonic acid, are frezen out in the heat exchanger. Such a heat exchanger is described in Belgian patent specification 527,602.

The air flows through the conduit 11 to the gas-fractionating column 1, in which it is fractionated in known manner. At the top of the column the low boiling fraction (nitrogen) is carried oi in the gaseous state through the conduit 12, the nitrogen flowing through the conduit 13 to the gas refrigerator 14 and being condensed in its condenser chamber. The produced condensate leaves the refrigerator through the conduit 13 and flows into the down pipe 16 in which a fluid column forms. In the rise pipes 18 and 19 a vapour bubble pumpng action is maintained by supplying thermal energy via elements 32 and 33 respectively, with the result that the condensed liquid is pumped up. The condensed liquid pumped up through the conduit 18 is supplied to the column and acts as a washing liquid in it. The ether part of the condensate leaves the system through the conduit 20 and the liquid look 21 and collects as a product in a receptacle (not shown). The high-boiling fraction, that is to say oxygen, produced in the column as a fluid through the pipe 4 into the column which invariably contains a certain quantity of liquid. Naturally, equilibrium has to be established between the amouut of oxygen supplied from the column to the boiler 2 and the amount of oxygen evaporation due the supply of thermal energy through the air. This is achieved by using a system of particular construction comprising pipe connections 22 and 23. If: the level of the liquid in the boiler is low, so that the pipe connection 23 opening into the boiler at a lower point protrudes from the level, a part of the produced vapour, which consists of an oxygen-nitrogen gas mixture rich in oxygen, will flow through the conduit 22. the down-part 24, the conduit 26 and the conduit 27 to the column 1. Another part of said gas mixture flows through the conduit 23, the down-portion 25, the conduit 26 and the conduit 27 likewise to the column. Since the temperature of said gas-mixture exceeds that of the nitrogen in the conduits 18 and 19 thermal energy will be supplied via strips 32 and 33 to the rise tubes 18 and 19 respectively, thus producing the aforesaid vapour bubble pumping action, that is to say a flow of cold occurs between said rise pipes 18 and 19, and the pipe connections 23 and 22 respectively. As a result of said flow of cold at least a part of the oxygen of the gasrnixture condenses and this condensate is carried back to the boiler through the conduits 29 and 30. The quantity of nitrogen supplied to the column through the rise pipe 18 is at least such that the level of the fluid in the boiler cannot drop far below the lower end of the conduit 23. If the liquid level rises in the boiler the conduit 23 is gradually closed on account of its end 31 out at an oblique angle. As a result the concentration of oxygen inside the pipe connection 23 varies, since the gas mixture becomes poorer in oxygen and consequently richer in nitrogen, particularly if the pipe connection 23 is completely closed by the rising level of the fluid. Owing to the variation in concentration the flow of cold from the rise. pipe 18 to the pipe connection 23 decreases, that is to say that the flow of thermal energy from.the pipe connection to the rise pipe likewise decreases. As a result the vapour bubble pumping action decreases in the rise pipe 18, so that less nitrogen is supplied as washing liquid to the column and consequently less fluid rich in oxygen is supplied to the boiler, hence the liquid level again drops in the boiler. Naturally, oxyin gas-concentration injthe ppe connection 23. following system the temperature is measured in the ppe connection and serves as an impetus to the control device.

gen contnues flowing through the conduit 22 to the column 1.

The cock 28 is adjusted in such manner that the pressure inside the boiler exceeds anospheric pressure so that the oxygen vapour is partially blown oi through the conduit 5 from the boiler and this oxygen co-acts in cooling the air supplied through the conduit 10. For a Satsfactory operation of the aforesaid regulating device the temperature of the medium, which supplies the flow of cold to the ppe connection opening at a lower point into the boiler, should be as constant as possible. In the present case, this is ensured by the use of liqud nitrogen.

In the system shown in Figures 3 and 4, parts corresponding to those shown in Figures 1 and 2 are designated by the same reference numerals.

The air to be separated is supplied through a conduit 34 after discarding its impurities. In the heat exchanger 35, the air is cooled by the oxygen leaving the boiler through a conduit 36. Subsequently, the air flows through a helically wound heat-exchanger 37 inside the boiler 2 and is finally supplied to the column through the conduit 11. The produced nitrogen flows through the conduit 12 and the conduit 13 to the gas refrigerator 14 in which the nitrogen is condensed, the condensate subsequently being supplied through the conduit 13 to the down-ppe 16 and forming a column with a level 38 under normal operating conditions. Flush with said normal level, there is provided an outlet port 39 connected with an outlet ppe 40 comprising a liqud-look 41. The down-ppe 16 leads to a container 17 with a rise ppe 18 which opens into the column. Similarly to Fig. 1, a vapour bubble pumping action is maintained in the rise ppe 18 and to this end thermal energy is suppled to the rise ppe by way of a strip 32.

The boiler has a wall 3 with a ppe 4 which extends into the liqud inside the boiler. The boiler is connected with the column through ppe connections 22 and 23 and conduits 26 and 27 with a cock 28. The ppe connection23 opens into the boiler at a lower point than does the ppe connection 22 and the rst-mentioned ppe connection is closed at its lower end. It is laterally furnished with a number of ports 42 situated above one another so that this conduit is gradually closed when the level of the liqud rises in the boiler. Through the strip 32 the ppe connection 23 is in heat-exchanging contact with the conduit 18. The operation of the system corresponds on the whole to that of the system shown in Figures 1 and 2.

If the level of the liqud rises in the boiler the ppe connection 23 is gradually closed so that, as has been stated above, the concentration of the gas-mixture in the ppe connection is changed and the flow of cold from the rise ppe to the ppe connection decreases and consequently also the flow of thermal energy to the rise ppe 18, hence the vapeur bubble pumping action inside the ppe 18 decreases and less liqud is supplied to the col umn. As a result the level of the liqud in the down ppe 16 rises, so that a larger amount of liqud is carried ol through the conduit 40 with the liqud look 41. The outlet port 39 is situated at such a point that under normal operatng conditions the desired amount of condensed liqud is carried oifrom the system.

. The system shown in Fig. 5 substantially corresponds to the systems shown in Figures l, 2 and 3, 4. Parts corresponding to those of preceding figures are designated by the same reference numerals. In the aforesaid constructions, the flow of"cold itself provided for the control of the amount of washing liqud supplied to the column. Alternatively, other factors may provde for said control inter alia the aforesaid variation In the The to be fractionatd flows through the conduit 10 to the heat-'exchangr constituted by the ppe 5 with fins 7 and, due to its being cooled, gives ofi its impurities to said heat-exchanger, after which the purified and cooled air is supplied through the conduit 11 to the column. The gaseous nitrogen produced in the column flows through the conduit 12 to the gas refrigerator 14 and is condensed. The condensate flows through a conduit 43 with a branch ppe 44 and to a chamber 45 which is connected with the column through a number of ports 46. The conduit 44 is connected throughastrip 32 to the pipe connection 23. The boiler furthermore comprises a ppe connection 22 which leads through a conduit 26 to the ppe connection 23 opening at a lower point into the boiler. Both ppe connections are connected with the column through a conduit 27 comprising a closure device (not shown). Into the charriber 45 extends a tube 47 with a liqud look, which tube is pivotally connected at one end to a tube 48 arranged to be turned below the level of the liqud inside the chamber 45. Through a connecting 1od system 50 the tube48 is coupled to a plate 52 secured to bellows 51. The space 53 defined by the bellows and the plate 52 communicates through a port 54 with a chainber 55 which is in turn connected with a conduit 56 of a vapour prcssure thermometer, the end 57 of which joins the ppe connection 23. The nitrogen in the conduit 44 serves as a sdurce of cold for the ppe connection 23, the temperature of said nitrogen substantially being constant.

When the level of the liqud rises the ppe connection 23 is gradually closed, so that the temperature in said ppe connection decreases and the pressure in the vapour pressure thermometer drops o. This results in that the plate 52 descends and the oblique end of the ppe 48 descends fiurther below the level of the liqud so that more liqud flows from the ppe 49 and is carried oi from the system through the ppe 47. As a result less washing liqud is supplied to the column and consequently less liqud is supplied to the boiler, so that the liqud level in the boiler drops again. Besides by means of a vapour pressure thermometer the temperature in side the tube or the temperature of the condensed liqud rnay alternatively be measured with the aid of other temperature measuring devices such as, for example, thermo-elemei1ts or by means of -a resistance thermometer. In these cases, a temperature variaton may i11- volve a variation of the amount of liqud supplied to the column.

In the system shown in Fig. 6 corresponding parts of {precedingfigures are designated by the saine reference numerals. The air to be fractionated is again supplied through a conduit 10 and cooled by fins 7, the cooled air again flowing through the conduit 11 to the column 1. Nitrogen from the column flows through the conduit 1 2 to the gas refrigerator 14 and the liqud condensed therein is partially supplied through the conduit 43 to the chamber 45. The conduit 43 comprises a br.nch

ppe 58 with a liqud look 59 which is connected with a vessel 50 through a conduit 58. 'Ihrough a strip 32 the vessel 60 is in heat-exchangng contact with the ppe connection 23 opening at a lower point into the boiler. The vessel 60 furthermbre comprises an overflow ppe 61 with a liqud look 62, which ppe is connected with a down-ppe 63 which in turn merges into a rise ppe 64. The vessel 60 furthermore comprises two vapeur conduits 65 and 66, the conduit 65 comprising a cock 67 and being connectedwith the conduit 12, while the conduit 66 leads to the chamber 55, the vessel 60 thus being connected with the space 53 inside the bellows.

A variation of the vapour pressure inside the vessel 60 consequently results in a displacement of the tube 48, similarly to the constnuctou shown in Fig. 5.. The rise 7 tube. 64 Iens into the cenduit 43 'and furthermre cem- Prises a brunch tube 65 Opening into the conduit 12.

The pip'e connectioris 22 and 23 for the supply of vapourfrom the boiler 2 te the column are net cennected together, but open each individually into the column, the ports 68 and 69 having such a size that the pressure inside the boiler is suifioiently high te blow the remainder of the oxygen vapeur through the pipe oi from the boiler, while the port 68 islarger than the port 69. Thesystem operates as follows:

Owing to the cold supplied by the gas refrigerater the nitrogen leaving the column is condensed, the cendensatebeing partially supplied as washng liquid threugh the"cenduit43 and the -chamber 45 te the column. The ether part flows through the conduit 58 into the vessl '60 where this liquid produces a flow of cold te the pipe connection 23. The vapeur produced in the ve5sel 60 is again supplied through the cenduit 65 and the conduit 12 te the gas refrigerator, the pressure in:-the chamber 60 being transferred threugh the conduit 66 te the plate 52 of the bellows 54 with the result that the tube 48 assumes a given position.

When the liquid level rises in the boiler 2 the flow of cold from the ves sel 60 te the pipe cennection 23 decreases, as stated above with the result that less uitrogen evaporates in the vessel 60 and the pressure drops in this vessel. This results in that the pressure below the plate 52 likewise drops so that the tube 48 descends farther belew the liquid level and more liquid is carried oi from the system threugh the conduit 47. As long as the pipe connection 23 is clesed a greater amount of gas naturally flows through the pipe cennection 22 te the column.

Owihg te lesser evaporation of nitrogen in the chamber60 the liquid level increases in this ch-amber until theliquicl is Carried oi from the vessel through the 'oVerflowpipe 61 and is suppl ied through the down-pipe 63 te the rise pipe 64. On accountof unavoidable insulation losses, a vapeur bubble pumping actien may ensue in the rise tube 64 so that the nitrogen is pumped 11p andentersthe cenduit 43, the develeped vapeur being carried back to the gas-refrigerater 14 through the conduit 65a. Since a lesser amount of nitrogen is supplied te the column the liquid level inside the boiler 2 will again drop se that the conduit 23 is re-epened at its;bottom end. The liquid locks 59 and 67 maintain the required pressure in the vessel 60, which pressure is adjusted by means of the cock 67.

The aoresaid systems comprse a gas-refrigerator for cooling the nitrogen from the column. 'Il1e term gasrefrigerator is here te be understeod te mean a sooalled refrigerator operating accerding to the reverscd hot-gas engine principle. Said refrigerators may be constructed inmany difierent ways, for example as a displacer enginc, a double-acting engine as an engine in which the cylinders comprising chamber of variable volumes subtend an angle, er as an engine in which the werking charnber is combined with chat of a. hot-gas engine. A d"c iuble-actng engirle is described, for example, in U.S. Pat. No. 2,486,081.

"I'he drawings represent a displacer engine which Will beexplaincd with reference te Fig. 7. The engine shewn in thisfigure comprisesa cylinder 70 in which a displacer 71 and a piston;78 -are adapted te reciprocate harinenically with a substantially constant phase difier- -erice. Tothis endthe dsplacr 71 is coupled through a connecting-rod system 73to a crank of a crank-shaft 74.while the piston 72 is ceupled through a connectionrodsj/stem 75 te cranks of the 831116 crank-shaft. 'Ihe .spce'76 abeve the displcer 71 is the so-called expansien chamber which cemmunicates through a freezer 77, a regenerater 7Sand a cooler 79 with a compressionchamber 80 between the displac'er and the piston.

fDherefrigratr is driven from an electric motor 81 and as; a result of the reciprocating motien of the displacer and the piston a gas, for example hydrogen er helium, in the :engine performs a thermodynamic cycle se that cold is produced and -another medium can be coolecl by meansof the freezer. For this purpose a condenser chamber 82 is provided, in which gas, for example the nitregen from a gas-fractienating column, is 'cendensed. Similarly te Figures 5 and 6, said uitregen may be supplied through the cenduit 12 te the condenser chamber 82 and drawn oi as condensed liquid through the cenduit 43.

- 'In the systems as descnibed hereinbefore it is naturally also pessible te use ether sources of cold, but these wll censiderably complicate the system in the majority ofcases. As a matter of fact, the use of the gas refrigerater permits the column te be constructed as a single column producing nitrogen of high purity, while the column is adapted te operate at atmespheric er substantially atmosphen'e pressure.

Whatcis claimed is:

1. A gas fractonating system comprising a gas fractonating column, a boiler in which at least a part of the high boling raction evaporates, a seurce of cold te condense the 10W boiling fractien, transport means conveying a part of said cendensed liquid as a washing liquid te said column and anether part being carried efl trom said system, a first cenduit connecting said column te said boiler and extending below the liquid level in said boiler, second and thrd conduits connectecl between the boiler and the column in order to transport vapor from the boiler to the column, said second and thrd conduits being in the form of an inverted U with one end adapted te be closed and opened by the rise and fall of liquid in the boiler and an outlet connecting said second and thrd conduits te said column, a thrd part of said cendensed liquid being in heat exchanging relationship with at least one ofthe second and thrd conduits, and means whereby the quantity of heat delivered by the U te said transport means determines the quantity of washing liquid delivered te the column.

2. A gas fractionating system comprising a gas fractienating column, a boiler in which at least a part of the;high beiling fractien evaperates, a source of cold te condense the 10W boiling fraction, transport means cenveying a part of said condensed liquid as a washing liquid te said column and another part being carried ofi frorn said system, a first conduit connecting said column te said boiler and extending below the liquid level in said boiler, second and thrd cenduits connected between the boiler and the column in order to transport vapor fren1 the boiler te the column, said second and thrd conduits being in the form of an inverted U with ene end adapted te be closed and opened by the rise and f all ofliquid in the boiler and an outlet connecting said second and thrd cenduits te said column, a thrd part of said condensed liquid being in heat exchanging relatienship with at least one of the second and thrd conduits, a condensatien wall asseciated with said one end of the inverted U, and a control mechanism whereby the quantity of heat delivered by the U te said transport means determines the quantity of washing liquid deliveredto the column 3. A gas fractionating system as clainied in claim 1 -fur ther comprising a c ontrol mechanism wherein the temperature in said ene end of the inverted U determines the amount of washing liquid by means of said C011l1'0l mechanism.

dense the low boilng frction, transport means conveying a part of said condensed liquid as a washing liquid to said column and another part being carried ol from said system, a first conduit connecting said column to said boiler and extending below the liquid level in said boiler, second and third conduits connected between the boiler and the column in order to transport vapor from the boiler to the column, said second and third conduits being in the form of an inverted U with one end adapted to be closed and opened by the rise and fall of liquid in the boiler and an outlet connecting said second and third conduits to said column, a third part of said condensed liquid ben g in heat exchanging relationship with at least one of the second and third conduits, a substantally vertcal ppe supplying washing liquid to the column by means of a vapor lift created by said heat exchanging relationship, and means whereby the quantity of heat delivered by the U to said transport means determines the quantity of Washing liquid delivered to the column.

6. A gas fractionating system as claimed in claim further comprising a second substantially vertical ppe wherein a vapor bubble pumping action occurs for carrying ofi a part of the condensed liquid from the system, said second vertical ppe being in heat exchanging contact with the other of said second and third conduits.

7. A gas fractionating system comprising a gas fractionating column, a boiler in which at least a part of the high boiling fracton evaporat6s, a source of cold to condense the low boiling fraction, transport means conveyto said column and another part being carried ofl from said system, a first conduit connecting said column to said boiler and extending below the liquid level in said boiler, second and third conduits connected between the boiler and the column in order to transport vapor from the boiler to the column, said second and third conduits being in the form of an inverted U with one end adapted to be closed and opened by the rise and fall of liquid in the boiler and an outlet connecting said second and third conduits to said column, a third part of said condensed liquid being in heat exchanging relationship with at least one of the second and third conduits, means whereby the quantit-y of heat delivered by the U to said 1ng a part of said condensed liquid as a washing liquid inside the boiler and wherein said condensed liquid produced in said system is conducted back to said boiler.

9. A gas fractionating system comprising a gas frac tionating column, a boiler in which at least a part of the high boiling fraction evaporates, a source of cold to condense the low boilng fraction, transport means conveying a part of said condensed liquid as a washing liquid to said column and another part being carried off from said system, a first conduit connecting said column to said boiler and extending below the liquid level in said boiler, second and third conduits connected between the boiler and the column in order to transport vapor from the boiler to the column, said second and third conduits being in the form of an inverted U with one end adapted to be closed and opened by the rise and fall of liquid in the boiler and an outlet connecting said second and third conduits to said column, said second conduit being so shapd so as to become gradually closed off when the liquid rises in the boiler, a third part of said condensed liquid being in heat exchanging relationship with at least one of the second and third conduits, and means whereby the quantity of heat delivered by the U to said transport means determincs the quantity of washing liquid delivered to the column.

10. A gas fractionating system as claimed in claim 9 wherein said second conduit has one end cut off at an oblique angle.

References Cited in the file of this patent UNITED STATES PATENTS 2,195976 Schlitt Apr. 2, 1940 2,431,866 Dennis Dec. 2, 1947 2,519892 Dennis Aug. 22, 1950 2527,623 Fausek Oct. 31, 1950 2672,031 Schilling Mar. 16, 1954 

